On any given day, pitch emails like the ones above come in. A search for “Bluetooth speaker” in my inbox returns nearly 250 exchanges over the past 18 months — and those are just the ones I haven’t deleted.

Run a search for “Bluetooth speakers” on Amazon.com, and there are more than 48,000 results. Browse on Apple.com or walk into an Apple store, and you will see at least 10 different brands of Bluetooth speakers being sold there.

So, why this deluge of Bluetooth speakers?

There are several reasons why these often-cheap gadgets are flooding the market and becoming almost as ubiquitous as headphones (one set for every occasion?), but first know this: They’re selling.

According to research group NPD, which tracks consumer product sales in the U.S., 740,000 Bluetooth-equipped speakers were sold in the first quarter of 2013, which was — wait for it — a 432 percent increase from a year ago.

From a dollar perspective, the market for these devices grew from around $60 million in 2011 to $264 million in 2012.

You might recall Jawbone’s marketing of the Jambox as the best-selling wireless speaker, but NPD says that, in 2012, the best-selling speaker was the $35 Jam from HMDX. Jambox speakers came in second, followed by Bose’s SoundLink Mobile.

The top factor cited when I asked industry experts about this Bluetooth explosion was “mobile.” All new smartphones and tablets have Bluetooth built in. It is, quite obviously, a way to play music and other audio out loud without having to tether an MP3 player, phone or tablet to a dock.

Another factor contributing to the category growth is that consumers’ perception of Bluetooth quality has changed, according to Liam Quirke, an analyst with IHS iSuppli. “Bluetooth audio suffered from an image crisis,” Quirke said. “You had the stereotypical Bluetooth headset user that people didn’t really want to be associated with. I think this inevitably had a bit of a knock-on effect in other audio devices.” He also noted that it used to be cumbersome to pair up electronics using Bluetooth.

Now, better implementations of Bluetooth and the use of new codecs to process data from audio files have improved the Bluetooth experience.

Quirke also notes what I’ll call the Apple effect: The company’s shift last year to a new connector in its phones and tablets forced some consumers to ditch their old 30-pin speaker docks and seek a wireless solution.

Lastly, Bluetooth speakers are relatively cheap for consumers. See the aforementioned $35 speaker, and consider the cost of installing a wired speaker system throughout your living room versus buying a few wirelessly connected, daisy-chained speakers.

At the same time, for hardware makers, “I have to think the margins are pretty high,” said Ben Arnold, analyst for the NPD Group. “Prices of the components have dropped, compared with a year or two years ago. If you have the right mix of brand (and) good-enough audio engineering, there is a lot of opportunity.”

Interestingly, Bluetooth speakers aren’t the only devices getting a boost from the explosion of mobile (and audio-streaming services). You might think they would totally supplant the “old-fashioned” dock, but the iPod dock market grew by 14 percent in 2012 from the year prior, and is still much bigger than the Bluetooth speaker market ($605 million in 2012). The headphone market grew 18 percent in 2012, and the premium segment — headphones that cost more than $100 — grew 62 percent.

Within a few years, Arnold said, the Bluetooth speaker market as we know it will change — sales of existing models could slow as consumers hit a limit on Bluetooth speakers. Unlike headphones, which audiophiles might own multiple pairs of for different listening environments, one can only have so many speakers in the home or office.

One area he pegs for growth is TV soundbars. A third of soundbar speakers sold in the first quarter of this year were Bluetooth-enabled, and Bluetooth could be coming to newer, premium TV models.

I’ll await the pitches for Bluetooth speakers that promise ear-drum blasting cinema sound from my TV, and until then, keep cleaning out the inbox.

Just as the atom bomb was the weapon that was supposed to render war obsolete, the Internet seems like capitalism’s ultimate feat of self-destructive genius, an economic doomsday device rendering it impossible for anyone to ever make a profit off anything again. It’s especially hopeless for those whose work is easily digitized and accessed free of charge.

— Author Tim Kreider on not getting paid for one’s work

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